16,871 research outputs found
Selective high frequency mechanical actuation driven by the VO2 electronic instability
Micro- and nano-electromechanical resonators are a fundamental building block
of modern technology, used in environmental monitoring, robotics, medical tools
as well as fundamental science. These devices rely on dedicated electronics to
generate their driving signal, resulting in an increased complexity and size.
Here, we present a new paradigm to achieve high-frequency mechanical actuation
based on the metal-insulator transition of VO, where the steep
variation of its electronic properties enables to realize high-frequency
electrical oscillations. The dual nature of this phase change, which is both
electronic and structural, turns the electrical oscillations into an intrinsic
actuation mechanism, powered by a small DC voltage and capable to selectively
excite the different mechanical modes of a microstructure. Our results pave the
way towards the realization of micro- and nano-electro-mechanical systems with
autonomous actuation from integrated DC power sources such as solar cells or
micro-batteries.Comment: Main text: 6 pages, 4 figures Supplemental Material: 16 pages, 7
section
A 64mW DNN-based Visual Navigation Engine for Autonomous Nano-Drones
Fully-autonomous miniaturized robots (e.g., drones), with artificial
intelligence (AI) based visual navigation capabilities are extremely
challenging drivers of Internet-of-Things edge intelligence capabilities.
Visual navigation based on AI approaches, such as deep neural networks (DNNs)
are becoming pervasive for standard-size drones, but are considered out of
reach for nanodrones with size of a few cm. In this work, we
present the first (to the best of our knowledge) demonstration of a navigation
engine for autonomous nano-drones capable of closed-loop end-to-end DNN-based
visual navigation. To achieve this goal we developed a complete methodology for
parallel execution of complex DNNs directly on-bard of resource-constrained
milliwatt-scale nodes. Our system is based on GAP8, a novel parallel
ultra-low-power computing platform, and a 27 g commercial, open-source
CrazyFlie 2.0 nano-quadrotor. As part of our general methodology we discuss the
software mapping techniques that enable the state-of-the-art deep convolutional
neural network presented in [1] to be fully executed on-board within a strict 6
fps real-time constraint with no compromise in terms of flight results, while
all processing is done with only 64 mW on average. Our navigation engine is
flexible and can be used to span a wide performance range: at its peak
performance corner it achieves 18 fps while still consuming on average just
3.5% of the power envelope of the deployed nano-aircraft.Comment: 15 pages, 13 figures, 5 tables, 2 listings, accepted for publication
in the IEEE Internet of Things Journal (IEEE IOTJ
Navigation of mini swimmers in channel networks with magnetic fields
Controlled navigation of swimming micro robots inside fluid filled channels is necessary for applications in living tissues and vessels. Hydrodynamic behavior inside channels and interaction with channel walls need to be understood well for successful design and control of these surgical-tools-to-be. In this study, two different mechanisms are used for forward and lateral motion: rotation of helices in the direction of the helical axis leads to forward motion in the viscous fluid, and rolling due to wall traction results with the lateral motion near the wall. Experiments are conducted using a magnetic helical swimmer having 1.5 mm in length and 0.5 mm in diameter placed inside two different glycerol-filled channels with rectangular cross sections. The strength, direction and rotational frequency of the externally applied rotating magnetic field are used as inputs to control the position and direction of the micro swimmer in Y- and T-shaped channels
Force feedback pushing scheme for micromanipulation applications
Pushing micro-objects using point contact provides
more flexibility and less complexity compared to pick
and place operation. Due to the fact that in micro-world
surface forces are much more dominant than inertial forces
and these forces are distributed unevenly, pushing through
the center of mass of the micro-object may not yield a pure
translational motion. In order to translate a micro-object, the
line of pushing should pass through the center of friction. In this
paper, a semi-autonomous scheme based on hybrid vision/force
feedback procedure is proposed to push micro-objects with
human assistance using a custom built tele-micromanipulation
setup to achieve translational motion. In the semi-autonomous
pushing process, velocity controlled pushing with force feedback
is realized along x-axis by the human operator while y-axis
orientation is undertaken automatically using visual feedback.
This way the desired line of pushing for the micro-object
is controlled to pass through the varying center of friction.
Experimental results are shown to prove nano-Newton range
force sensing, scaled bilateral teleoperation with force feedback
and snapshot of pushing operation
Scale-dependent fracture in gradient elastic materials
Micro-electromechanical systems (MEMS) and Nano-electromechanical systems (NEMS) have a wide range of applications in aerospace, power industry, automation & robotics, chemical & medical treatment analysis, information technology and in the infrastructure health monitoring equipments. To ensure the reliability of such small devices, the mechanical and hence fracture behaviour of their common building blocks such as beams, tubes, and plates should be carefully evaluated. However, on a smaller scale, the microstructural effects such as size effects, load-induced and geometrically prompted stress singularities are more noticeable, particularly at the micro/nano scale. Classical continuum elasticity theories are inadequate to accurately describe the situations controlled by the microstructure effects since the influence of these effects are not properly accounted for. On the other hand, the higher order gradient theories such as strain gradient theory may effectively describe the effects of microstructure through the solution of properly formulated boundary value problems. Moreover, when dealing with piezoelectric micro/nano materials, due to the presence of massive strain gradient, the electric field-strain gradient coupling (flexoelectricity) should also be considered. The objective of this research is to evaluate the scale-dependent fracture behaviour of gradient elastic materials using strain gradient theory. In particular, two most widely studied geometrical configurations i.e. double cantilever beam (DCB) and centrally cracked material layer are employed in this work. The findings presented in this thesis are expected to give useful insights to those working in the structural integrity analysis at the micro/nano scale. They are anticipated to help in the design of micro/nano structural components and serve as a benchmark for future theoretical and empirical studies
Semi-autonomous scheme for pushing micro-objects
-In many microassembly applications, it is often
desirable to position and orient polygonal micro-objects lying on
a planar surface. Pushing micro-objects using point contact provides
more flexibility and less complexity compared to pick and
place operation. Due to the fact that in micro-world surface forces
are much more dominant than inertial forces and these forces
are distributed unevenly, pushing through the center of mass of
the micro-object will not yield a pure translational motion. In
order to translate a micro-object, the line of pushing should pass
through the center of friction. In this paper, a semi-autonomous
scheme based on hybrid vision/force feedback is proposed to push
microobjects with human assistance using a custom built telemicromanipulation
setup to achieve pure translational motion.
The pushing operation is divided into two concurrent processes:
In one process human operator who acts as an impedance
controller alters the velocity of the pusher while in contact with
the micro-object through scaled bilateral teleoperation with force
feedback. In the other process, the desired line of pushing for
the micro-object is determined continuously using visual feedback
procedures so that it always passes through the varying center of
friction. Experimental results are demonstrated to prove nanoNewton
range force sensing, scaled bilateral teleoperation with
force feedback and pushing microobjects
- …